Engines have, in the past, utilized multiple air inlets to feed air to airboxes. Using multiple inlets provides a high flowrate of filtered air to internal combustion engines. High intake flowrates may be particularly desirable in compression ignition engines, which may require during certain operating conditions, a large amount of intake airflow to drive combustion. However, depending on the location of the air inlet the inlet may be susceptible to damage, clogging, etc., from external road debris (e.g., snow, ice, rocks, etc.).
Previous intake systems have attempted to protect air inlets by placing the inlet in a more shielded vehicle location to reduce the inlet's exposure to road debris. One example approach shown by MacKenzie et al., in U.S. Pat. No. 9,062,639, is a dual inlet air induction system. In MacKenzie's air induction system, one air inlet is positioned under an engine compartment hood and another air inlet is located in a fender panel. The inventors have recognized several drawbacks with MacKenzie's system. For instance, in MacKenzie's system, the inlet positioned under the hood receives air at elevated temperatures, due to the inlet's proximity to hot engine components. Elevated intake air temperatures can decrease combustion efficiency and in some cases may lead to pre-ignition, knock, etc. Therefore, MacKenzie's system as well as other intake systems have in the past made tradeoffs between the degree of air inlet shielding and the temperature of the air drawn into the inlet.
Other attempts have been made to actively control airflow through different air inlets. For instance, one example approach shown by Miller et al., in U.S. Pat. No. 8,048,179, includes an intake system having two air inlets with one of the inlets having a flow valve positioned therein. The valve is opened during cold weather conditions to draw hot air into a portion of the intake system that may be obstructed by snow. However, the active control system, described in Miller, may be prone to malfunction or in some cases failure due to the complexity of the control system used to adjust the flow valve. Furthermore, active flow valves may be costly and as a result the production costs of vehicles using active valves may be unduly increased. Additionally, Miller's system only allows a single airflow path to be opened at any one time.
The inventors have recognized the aforementioned problems and confronting these problems developed an air intake system. The air intake system includes a first air inlet duct providing intake air to an engine intake conduit. The first air inlet duct includes an opening positioned external to an engine compartment. The air intake system also includes a second air inlet duct positioned upstream of the engine intake conduit and external to the engine compartment. The second air inlet duct includes a foam plug selectively impeding airflow through the second air inlet duct and the foam plug spans an opening of the second air inlet duct. In this way, one air inlet may provide air to the engine regardless of operating conditions, on the one hand. While on the other hand, another air inlet can provide selective airflow to the engine. The foam plug in the second air inlet enables an increase in airbox inflow, during low hazard conditions. Conversely, during high hazard conditions (e.g., cold weather), the foam plug inhibits airflow through an exposed air inlet duct to reduce the likelihood of damage to the system caused by external debris.
In one example, the second air inlet duct may be positioned in a less protected location than the first air inlet duct to enable an increased amount of air to be drawn into the second duct. For instance, the second air inlet duct may be positioned below and/or in a more forward location than the first air inlet duct. In this way, the second air inlet duct may draw in a large amount of low temperature air when the foam plug is above a threshold temperature. Consequently, the air intake system may provide a greater amount of airflow to the engine, to increase combustion efficiency, when inclement conditions are not occurring. Conversely, during snowy conditions, for instance, the foam plug may adapt to block the second air inlet duct to prevent snow, ice, etc., from entering the air intake system. Consequently, the air intake system can be protected from external debris during selected conditions, thereby decreasing the likelihood of engine degradation and in some cases shutdown during inclement conditions. Moreover, the foam plug may be less costly and more robust than mechanical flow control valves that act to block inlet conduits during inclement conditions. Consequently, the manufacturing costs of the system may be reduced when a foam plug is incorporated into an inlet duct.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.